Officers and cars respond to urgent calls; or all calls, depending on how the TARDIS is feeling.
Anyway, my thoughts on the story will be appearing at the Doctor Who News Page reviews section, I hope, in the not-too-distant future. They are generally positive.
ETA:
Here's the review: apologies for the lack of formatting and the use of 'St John' rather than the canonical 'Saint John'.
Also posted at
http://sir-guinglain.dreamwidth.org/591882.html.